Overlapping homologous superfamilies

Domain relationships

Description

This domain is found in archaeal, bacterial and eukaryotic proteins.

In the archaea and bacteria, they are primarily restricted to the euryarchaeota and proteobacteria respectively; where they are either described as either nucleolar protein or tRNA/rRNA cytosine-C5-methylase. They all have the S-adenosyl methionine (SAM) binding domain and are related to bacterial Fmu (16S rRNA m5C 967 methyltransferase) where the structure of the methyl transferase domain has been determined [PMID: 14656444].

In the eukaryota, the majority are annotated as being 'nucleolar protein'. None of the eukaryotic members in this family have a the SAM binding signature. Despite this, the yeast Nop2p is a probable RNA m(5)C methyltransferase, essential for processing and maturation of 27S pre-rRNA and large ribosomal subunit biogenesis [PMID: 12872006]; localised to the nucleolus and is essential for viability [PMID: 7806561]. Reduced Nop2p expression limits yeast growth and decreases levels of mature 60S ribosomal subunits while altering rRNA processing [PMID: 8972218]. There is substantial identity between Nop2p and human p120 (NOL1), which is also called the proliferation-associated nucleolar antigen [PMID: 7806561, PMID: 2576976].